Question

I’m pulling stock-quotes from Yahoo into a named tuple using the CSV module.

YahooQuote = collections.namedtuple(
    'YahooQuote', 'date, open, high, low, close, volume, adj_close')

def prices(ticker):
    # make url given ticker
    csvfile = urllib2.urlopen(url) 
    return map(YahooQuote._make, csv.reader(csvfile))

Yahoo’s stock quote csv format does not include the stock ticker. If I adjusted my named tuple class to include a ticker attribute, how would I modify the map expression to make it add the value of the ticker argument to each of the named tuple instances?

Answer 1

I’m genetically incapable of understanding code with map() in it, so I’m just going to transform “map(f, i)” into “[f(x) for x in i]” so I don’t have to:

return [YahooQuote._make(x) for x in csv.reader(csvfile)]

Then it’s a simple matter to add ticker to the end of the lists returned by csv.reader:

YahooQuote = collections.namedtuple(
    'YahooQuote', 'date, open, high, low, close, volume, adj_close, ticker')

def prices(ticker):
    # make url given ticker
    ticker_list = [ticker]
    csvfile = urllib2.urlopen(url) 
    return [YahooQuote._make(x + ticker_list) for x in csv.reader(csvfile)]